This is a collection of notes on GBA/NDS-related homebrew development.
"Slot 2" Hardware
General Information - Compact Flash Adapters
Compact Flash adapters on the GBA cartridge interface all generally work by exposing IDE registers using the top eight address bits coupled with the sixteen-bit data bus, wiring them directly to the relevant IDE connector pins.
In programmer-facing documentation, the two address ranges mentioned (matching PC I/O) are 1F0h-1F7h and 3F0-3F7h. In hardware, the choice is controled by Chip Select (CS) pins, while the specific register is chosen using DA0-DA2.
- Is INTRQ relayed in any way? On which adapters?
Cartridge - Memory Expansion Pak
- 0B4h (device type) == 24h
- 0BFh - bit 7 clear
- 1FFFFh - bit 7 clear
Official software uses default timings (EXMEMCNT[6:0] = 00h).
- 240000h - unlock register (32-bit)
- bit 0 - set if unlocked, clear if locked
- bit 1-31 - unknown
- 1000000h - 8 megabytes of memory starts here
- what are the remaining unlock register bits?
- official software crashes if any bits 16-31 are set on initialization
- does the unlock register control memory visibility or just writability?
Cartridge - GBA Movie Player
Compact Flash interface:
|Address bits||Map to|
|22||Chip Select 0/1|